280 ON THE CLASSIFICATION OP BIRDS. 
trary is the fact. This inequality of size^ and difference 
of colour, in the sexes, renders it very difficult to de- 
termine the species ; and this difficulty is increased by 
the length of time required for the young birds to as- 
sume their adult plumage, which is often totally different 
from that which they at first put on. Rapacious birds 
are immediately recognised by their strong hooked bill, 
and formidably acute talons : by these instruments of 
rapine they are enabled to despatch and prey upon ani- 
mals little inferior in size to themselves. In these attacks 
the victim is first struck by the talons, or by the feet, 
the muscles of which indicate extraordinary strength. 
The prey once secured, the bill is then used, as a knife, 
to separate or tear the parts asunder : for this purpose 
there is placed a strong and sharp tooth in one or both 
mandibles, which materially assists the operation. In 
such tribes as feed upon carrion, or small animals, this 
tooth, being no longer essential, is either obsolete or 
entirely wanting. It is thus that nature preserves, in 
this order, a strong analogy to the carnivorous quadru- 
peds. The slothful vulture and the cowardly hyena 
glut themselves upon carrion ; the bold and majestic 
lions, like the noble falcons, feast upon no other prey 
than what their own courage has procured ; while the 
owls and the stoats prowl during the night after the 
same feeble and ignoble game. 
• (232.) The order before us is composed of only three 
families that are now in existence, whose prominent 
features are, perhaps, more decided than those of any 
other groups in ornithology : the vultures, the falcons, 
and the owls are so strongly marked as to be familiar to 
every one. It has been customary with some system- 
atists to divide this order into two groups, from the 
period of their feeding ; the two former being diurnal, 
and the latter nocturnal : but this explains little. A 
much clearer, and certainly a more correct, idea will be 
formed of their true nature, by considering them with 
reference to their attributes, and their natural affinities. 
(233.) Commencing with the Vultubid.®, or FuL 
